The present invention is directed to a process for bonding articles of specific polymers to other articles with an adhesion promoter. More specifically, the present invention is directed to a process for bonding an article comprising a polymer having photosensitivity-imparting substituents to a second article comprising metal, silicon, plasma nitride, or glass with an adhesion promoter which is a titanium, zirconium, or silicon compound. One embodiment of the present invention is directed to a process for bonding a first article to a second article which comprises (a) providing a first article comprising a polymer having photosensitivity-imparting substituents; (b) providing a second article comprising metal, plasma nitride, silicon, or glass; (c) applying to at least one of the first article and the second article an adhesion promoter selected from silanes, titanates, or zirconates having (i) alkoxy, aryloxy, or arylalkyloxy functional groups and (ii) functional groups including at least one photosensitive aliphatic  greater than Cxe2x95x90C less than  linkage; (d) placing the first article in contact with the second article; and (e) exposing the first article, second article, and adhesion promoter to radiation, thereby bonding the first article to the second article with the adhesion promoter. Another embodiment of the present invention is directed to an ink jet printhead which comprises (i) an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles, (ii) a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes formed thereon, at least a portion of said surface comprising metal, plasma nitride, silicon, or glass, and (iii) an insulative layer deposited on the surface of the lower substrate and over the heating elements and addressing electrodes and patterned to form recesses therethrough to expose the heating elements and terminal ends of the addressing electrodes, the upper and lower substrates being aligned, mated, and bonded together to form the printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles, said insulative layer comprising a crosslinked or chain extended polymer wherein the crosslinking or chain extension is at least partly through photosensitivity-imparting substituents; said insulative layer being bonded to the surface of the lower substrate with an adhesion promoter selected from silanes, titanates, or zirconates having (a) alkoxy, aryloxy, or arylalkyloxy functional groups and (b) functional groups including at least one photosensitive aliphatic  greater than Cxe2x95x90C less than  linkage. Yet another embodiment of the present invention is directed to a process for forming an ink jet printhead which comprises (a) providing a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes having terminal ends formed thereon, at least a portion of said surface comprising metal, plasma nitride, silicon, or glass; (b) depositing onto the surface of the lower substrate having the heating elements and addressing electrodes thereon an adhesion promoter selected from silanes, titanates, or zirconates having (i) alkoxy, aryloxy, or arylalkyloxy functional groups and (ii) functional groups including at least one photosensitive aliphatic  greater than Cxe2x95x90C less than  linkage; (c) depositing onto the surface of the lower substrate having the adhesion promoter thereon an insulative layer comprising a polymer having photosensitivity-imparting substituents, provided that the R2 group of the adhesion promoter contains a functional group which is capable of reacting with the material selected for the insulative layer; (d) exposing the adhesion promoter and the insulative layer to actinic radiation in an imagewise pattern such that the polymer comprising the insulative layer in exposed areas becomes crosslinked or chain extended and the polymer in unexposed areas does not become crosslinked or chain extended, wherein the unexposed areas correspond to areas of the lower substrate having thereon the heating elements and the terminal ends of the addressing electrodes, and wherein the insulative layer is bonded to the lower substrate with the adhesion promoter in exposed areas; (e) removing the adhesion promoter and the polymer from the unexposed areas, thereby forming recesses in the layer, said recesses exposing the heating elements and the terminal ends of the addressing electrodes; (f) providing an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles; and (g) aligning, mating, and bonding the upper and lower substrates together to form a printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles, thereby forming a thermal ink jet printhead. Still another embodiment of the present invention is directed to an ink jet printhead which comprises (i) an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles, (ii) a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes formed thereon, at least a portion of said surface comprising metal, plasma nitride, silicon, or glass, and (iii) an insulative layer deposited on the surface of the lower substrate and over the heating elements and addressing electrodes and patterned to form recesses therethrough to expose the heating elements and terminal ends of the addressing electrodes, the upper and lower substrates being aligned, mated, and bonded together to form the printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles, said insulative layer comprising (a) a crosslinked or chain extended polymer wherein the crosslinking or chain extension is at least partly through photosensitivity-imparting substituents, and (b) an adhesion promoter selected from silanes, titanates, or zirconates having (1) alkoxy, aryloxy, or arylalkyloxy functional groups and (2) functional groups including at least one photosensitive aliphatic  greater than Cxe2x95x90C less than  linkage. Another embodiment of the present invention is directed to a process for forming an ink jet printhead which comprises (a) providing a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes having terminal ends formed thereon, at least a portion of said surface comprising metal, plasma nitride, silicon, or glass; (b) depositing onto the surface of the lower substrate an insulative layer comprising (i) a polymer having photosensitivity-imparting substituents, and (ii) an adhesion promoter selected from silanes, titanates, or zirconates having (A) alkoxy, aryloxy, or arylalkyloxy functional groups and (B) functional groups including at least one photosensitive aliphatic  greater than Cxe2x95x90C less than  linkage; (c) exposing the insulative layer to actinic radiation in an imagewise pattern such that the polymer comprising the insulative layer in exposed areas becomes crosslinked or chain extended and the polymer in unexposed areas does not become crosslinked or chain extended, wherein the unexposed areas correspond to areas of the lower substrate having thereon the heating elements and the terminal ends of the addressing electrodes, and wherein the insulative layer is bonded to the lower substrate in exposed areas; (d) removing the adhesion promoter and the polymer from the unexposed areas, thereby forming recesses in the layer, said recesses exposing the heating elements and the terminal ends of the addressing electrodes; (e) providing an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles; and (f) aligning, mating, and bonding the upper and lower substrates together to form a printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles, thereby forming a thermal ink jet printhead.
In microelectronics applications, such as microelectrical mechanical systems (MEMS), there is a great need for low dielectric constant, high glass transition temperature, thermally stable, photopatternable polymers for use as interlayer dielectric layers and as passivation layers which protect microelectronic circuitry. Poly(imides) are widely used to satisfy these needs; these materials, however, have disadvantageous characteristics such as relatively high water sorption and hydrolytic instability. There is thus a need for high performance polymers which can be effectively photopatterned and developed at high resolution.
One particular application for such materials is the fabrication of ink jet printheads. Ink jet printing systems generally are of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field which adjusts the trajectory of each droplet in order to direct it to a gutter for recirculation or a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled unless it is to be placed on the recording medium.
Since drop-on-demand systems require no ink recovery, charging, or deflection, the system is much simpler than the continuous stream type. There are different types of drop-on-demand ink jet systems. One type of drop-on-demand system has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. The relatively large size of the transducer prevents close spacing of the nozzles, and physical limitations of the transducer result in low ink drop velocity. Low drop velocity seriously diminishes tolerances for drop velocity variation and directionality, thus impacting the system""s ability to produce high quality copies. Drop-on-demand systems which use piezoelectric devices to expel the droplets also suffer the disadvantage of a slow printing speed.
The other type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets and allows very close spacing of nozzles. The major components of this type of drop-on-demand system are an ink filled channel having a nozzle on one end and a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink in the immediate vicinity to vaporize almost instantaneously and create a bubble. The ink at the orifice is forced out as a propelled droplet as the bubble expands. When the hydrodynamic motion of the ink stops, the process is ready to start all over again. With the introduction of a droplet ejection system based upon thermally generated bubbles, commonly referred to as the xe2x80x9cbubble jetxe2x80x9d system, the drop-on-demand ink jet printers provide simpler, lower cost devices than their continuous stream counterparts, and yet have substantially the same high speed printing capability.
The operating sequence of the bubble jet system begins with a current pulse through the resistive layer in the ink filled channel, the resistive layer being in close proximity to the orifice or nozzle for that channel. Heat is transferred from the resistor to the ink. The ink becomes superheated far above its normal boiling point, and for water based ink, finally reaches the critical temperature for bubble formation or nucleation of around 280xc2x0 C. Once nucleated, the bubble or water vapor thermally isolates the ink from the heater and no further heat can be applied to the ink. This bubble expands until all the heat stored in the ink in excess of the normal boiling point diffuses away or is used to convert liquid to vapor, which removes heat due to heat of vaporization. The expansion of the bubble forces a droplet of ink out of the nozzle, and once the excess heat is removed, the bubble collapses. At this point, the resistor is no longer being heated because the current pulse has passed and, concurrently with the bubble collapse, the droplet is propelled at a high rate of speed in a direction towards a recording medium. The surface of the printhead encounters a severe cavitational force by the collapse of the bubble, which tends to erode it. Subsequently, the ink channel refills by capillary action. This entire bubble formation and collapse sequence occurs in about 10 microseconds. The channel can be refired after 100 to 500 microseconds minimum dwell time to enable the channel to be refilled and to enable the dynamic refilling factors to become somewhat dampened. Thermal ink jet equipment and processes are well known and are described in, for example, U.S. Pat. No. 4,601,777, U.S. Pat. No. 4,251,824, U.S. Pat. No. 4,410,899, U.S. Pat. No. 4,412,224, U.S. Pat. No. 4,532,530, and U.S. Pat. No. 4,774,530, the disclosures of each of which are totally incorporated herein by reference.
The present invention is suitable for ink jet printing processes, including drop-on-demand systems such as thermal ink jet printing, piezoelectric drop-on-demand printing, and the like.
In ink jet printing, a printhead is usually provided having one or more ink-filled channels communicating with an ink supply chamber at one end and having an opening at the opposite end, referred to as a nozzle. These printheads form images on a recording medium such as paper by expelling droplets of ink from the nozzles onto the recording medium. The ink forms a meniscus at each nozzle prior to being expelled in the form of a droplet. After a droplet is expelled, additional ink surges to the nozzle to reform the meniscus.
In thermal ink jet printing, a thermal energy generator, usually a resistor, is located in the channels near the nozzles a predetermined distance therefrom. The resistors are individually addressed with a current pulse to momentarily vaporize the ink and form a bubble which expels an ink droplet. As the bubble grows, the ink bulges from the nozzle and is contained by the surface tension of the ink as a meniscus. The rapidly expanding vapor bubble pushes the column of ink filling the channel towards the nozzle. At the end of the current pulse the heater rapidly cools and the vapor bubble begins to collapse. However, because of inertia, most of the column of ink that received an impulse from the exploding bubble continues its forward motion and is ejected from the nozzle as an ink drop. As the bubble begins to collapse, the ink still in the channel between the nozzle and bubble starts to move towards the collapsing bubble, causing a volumetric contraction of the ink at the nozzle and resulting in the separation of the bulging ink as a droplet. The acceleration of the ink out of the nozzle while the bubble is growing provides the momentum and velocity of the droplet in a substantially straight line direction towards a recording medium, such as paper.
Ink jet printheads include an array of nozzles and may, for example, be formed of silicon wafers using orientation dependent etching (ODE) techniques. The use of silicon wafers is advantageous because ODE techniques can form structures, such as nozzles, on silicon wafers in a highly precise manner. Moreover, these structures can be fabricated efficiently at low cost. The resulting nozzles are generally triangular in cross-section. Thermal ink jet printheads made by using the above-mentioned ODE techniques typically comprise a channel plate which contains a plurality of nozzle-defining channels located on a lower surface thereof bonded to a heater plate having a plurality of resistive heater elements formed on an upper surface thereof and arranged so that a heater element is located in each channel. The upper surface of the heater plate typically includes an insulative layer which is patterned to form recesses exposing the individual heating elements. This insulative layer is referred to as a xe2x80x9cpit layerxe2x80x9d and is sandwiched between the channel plate and heater plate. For examples of printheads employing this construction, see U.S. Pat. No. 4,774,530 and U.S. Pat. No. 4,829,324, the disclosures of each of which are totally incorporated herein by reference. Additional examples of thermal ink jet printheads are disclosed in, for example, U.S. Pat. No. 4,835,553, U.S. Pat. No. 5,057,853, and U.S. Pat. No. 4,678,529, the disclosures of each of which are totally incorporated herein by reference.
In thermal ink jet printheads, polyimides are commonly used for electronic passivation and for defining the fluid path. The polyimide layer typically is bonded between the channel plate, which frequently is fabricated of silicon, and the heater wafer. In many instances, a trialkoxysilane based coupling agent is used to promote adhesion of the polyimide to the heater wafer, which often is passivated with materials such as phosphosilicate glass. The principle mechanism by which the silane coupling agent works is condensation of the silane with polar hydroxy groups that exist on the phosphosilicate glass surface. Prior to deposition onto the heater wafer substrate, the trialkoxysilane can be converted to the trisilanol (HO)3SiR form. The silane is spin cast onto the hydroxyl covered substrate and heated. The condensation reaction produces water and/or alcohol reaction products when Sixe2x80x94Oxe2x80x94Si bonds form. Although Sixe2x80x94Oxe2x80x94Si is a strong covalent bond, under acidic or basic conditions the condensation/hydrolysis equilibrium can be pushed toward hydrolysis, and delamination can occur. For effective silane-based adhesion promotion, an adequate number of substrate-polymer bonds must form in addition to a highly 2D or 3D crosslinked siloxane network. In this instance, the probability that all Sixe2x80x94Oxe2x80x94Si bonds will hydrolyze simultaneously is reduced.
U.S. Pat. No. 5,739,254, filed Aug. 29, 1996, entitled xe2x80x9cProcess for Haloalkylation of High Performance Polymers,xe2x80x9d with the named inventors Timothy J. Fuller, Ram S. Narang, Thomas W. Smith, David J. Luca, and Raymond K. Crandall, and European Patent Publication 0,826,700, the disclosures of each of which are totally incorporated herein by reference, disclose a process which comprises reacting a polymer of the general formula 
wherein x is an integer of 0 or 1, A is one of several specified groups, such as 
B is one of several specified groups, such as 
or mixtures thereof, and n is an integer representing the number of repeating monomer units, with an acetyl halide and dimethoxymethane in the presence of a halogen-containing Lewis acid catalyst and methanol, thereby forming a haloalkylated polymer. In a specific embodiment, the haloalkylated polymer is then reacted further to replace at least some of the haloalkyl groups with photosensitivity-imparting groups. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned polymer.
U.S. Pat. No. 5,738,799, filed Sep. 12, 1996, the disclosure of which is totally incorporated herein by reference, discloses an ink-jet printhead fabrication technique which enables capillary channels for liquid ink to be formed with square or rectangular cross-sections. A sacrificial layer is placed over the main surface of a silicon chip, the sacrificial layer being patterned in the form of the void formed by the desired ink channels. A permanent layer, comprising permanent material, is applied over the sacrificial layer, and, after polishing the two layers to form a uniform surface, the sacrificial layer is removed. Preferred materials for the sacrificial layer include polyimide while preferred materials for the permanent layer include polyarylene ether, although a variety of material combinations are possible.
Copending application U.S. Ser. No. 08/705,914, filed Aug. 29, 1996, entitled xe2x80x9cThermal Ink Jet Printhead With Ink Resistant Heat Sink Coating,xe2x80x9d with the named inventors Ram S. Narang and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses a heat sink for a thermal ink jet printhead having improved resistance to the corrosive effects of ink by coating the surface of the heat sink with an ink resistant film formed by electrophoretically depositing a polymeric material on the heat sink surface. In one described embodiment, a thermal ink jet printer is formed by bonding together a channel plate and a heater plate. Resistors and electrical connections are formed in the surface of the heater plate. The heater plate is bonded to a heat sink comprising a zinc substrate having an electrophoretically deposited polymeric film coating. The film coating provides resistance to the corrosion of higher pH inks. In another embodiment, the coating has conductive fillers dispersed therethrough to enhance the thermal conductivity of the heat sink. In one embodiment, the polymeric material is selected from the group consisting of polyethersulfones, polysulfones, polyamides, polyimides, polyamide-imides, epoxy resins, polyetherimides, polyarylene ether ketones, chloromethylated polyarylene ether ketones, acryloylated polyarylene ether ketones, polystyrene and mixtures thereof.
Copending application U.S. Ser. No. 08/703,138, filed Aug. 29, 1996, entitled xe2x80x9cMethod for Applying an Adhesive Layer to a Substrate Surface,xe2x80x9d with the named inventors Ram S. Narang, Stephen F. Pond, and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses a method for uniformly coating portions of the surface of a substrate which is to be bonded to another substrate. In a described embodiment, the two substrates are channel plates and heater plates which, when bonded together, form a thermal ink jet printhead. The adhesive layer is electrophoretically deposited over a conductive pattern which has been formed on the binding substrate surface. The conductive pattern forms an electrode and is placed in an electrophoretic bath comprising a colloidal emulsion of a preselected polymer adhesive. The other electrode is a metal container in which the solution is placed or a conductive mesh placed within the container. The electrodes are connected across a voltage source and a field is applied. The substrate is placed in contact with the solution, and a small current flow is carefully controlled to create an extremely uniform thin deposition of charged adhesive micelles on the surface of the conductive pattern. The substrate is then removed and can be bonded to a second substrate and cured. In one embodiment, the polymer adhesive is selected from the group consisting of polyamides, polyimides, polyamide-imides, epoxy resins, polyetherimides, polysulfones, polyether sulfones, polyarylene ether ketones, polystyrenes, chloromethylated polyarylene ether ketones, acryloylated polyarylene ether ketones, and mixtures thereof.
Copending application U.S. Ser. No. 08/697,750, filed Aug. 29, 1996, entitled xe2x80x9cElectrophoretically Deposited Coating For the Front Face of an Ink Jet Printhead,xe2x80x9d with the named inventors Ram S. Narang, Stephen F. Pond, and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses an electrophoretic deposition technique for improving the hydrophobicity of a metal surface, in one embodiment, the front face of a thermal ink jet printhead. For this example, a thin metal layer is first deposited on the front face. The front face is then lowered into a colloidal bath formed by a fluorocarbon-doped organic system dissolved in a solvent and then dispersed in a non-solvent An electric field is created and a small amount of current through the bath causes negatively charged particles to be deposited on the surface of the metal coating. By controlling the deposition time and current strength, a very uniform coating of the fluorocarbon compound is formed on the metal coating. The electrophoretic coating process is conducted at room temperature and enables a precisely controlled deposition which is limited only to the front face without intrusion into the front face orifices. In one embodiment, the organic compound is selected from the group consisting of polyimides, polyamides, polyamide-imides, polysulfones, polyarylene ether ketones, polyethersulfones, polytetrafluoroethylenes, polyvinylidene fluorides, polyhexafluoro-propylenes, epoxies, polypentafluorostyrenes, polystyrenes, copolymers thereof, terpolymers thereof, and mixtures thereof.
Copending application U.S. Ser. No. 08/705,916, filed Aug. 29, 1996, entitled xe2x80x9cStabilized Graphite Substrates,xe2x80x9d with the named inventors Gary A. Kneezel, Ram S. Narang, Timothy J. Fuller, and Peter J. John, the disclosure of which is totally incorporated herein by reference, discloses an apparatus which comprises at least one semiconductor chip mounted on a substrate, said substrate comprising a graphite member having electrophoretically deposited thereon a coating of a polymeric material. In one embodiment, the semiconductor chips are thermal ink jet printhead subunits. In one embodiment, the polymeric material is of the general formula 
wherein x is an integer of 0 or 1, A is one of several specified groups, such as 
B is one of several specified groups, such as 
or mixtures thereof, and n is an integer representing the number of repeating monomer units.
Copending application U.S. Ser. No. 08/705,375, filed Aug. 29, 1996, entitled xe2x80x9cImproved Curable Compositions,xe2x80x9d with the named inventors Timothy J. Fuller, Ram S. Narang, Thomas W. Smith, David J. Luca, and Ralph A. Mosher, and European Patent Publication 0,827,027, the disclosures of each of which are totally incorporated herein by reference, disclose an improved composition comprising a photopatternable polymer containing at least some monomer repeat units with photosensitivity-imparting substituents, said photopatternable polymer being of the general formula 
wherein x is an integer of 0 or 1, A is one of several specified groups, such as 
B is one of several specified groups, such as 
or mixtures thereof, and n is an integer representing the number of repeating monomer units. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned polymer and a thermal ink jet printhead containing therein a layer of a crosslinked or chain extended polymer of the above formula.
Copending application U.S. Ser. No. 08/705,365, filed Aug. 29, 1996, entitled xe2x80x9cHydroxyalkylated High Performance Curable Polymers,xe2x80x9d with the named inventors Ram S. Narang and Timothy J. Fuller, and European Patent Publication 0,827,028, the disclosures of each of which are totally incorporated herein by reference, disclose a composition which comprises (a) a polymer containing at least some monomer repeat units with photosensitivity-imparting substituents which enable crosslinking or chain extension of the polymer upon exposure to actinic radiation, said polymer being of the formula 
wherein x is an integer of 0 or 1, A is one of several specified groups, such as 
B is one of several specified groups, such as 
or mixtures thereof, and n is an integer representing the number of repeating monomer units, wherein said photosensitivity-imparting substituents are hydroxyalkyl groups; (b) at least one member selected from the group consisting of photoinitiators and sensitizers; and (c) an optional solvent. Also disclosed are processes for preparing the above polymers and methods of preparing thermal ink jet printheads containing the above polymers.
Copending application U.S. Ser. No. 08/705,488, filed Aug. 29, 1996, entitled xe2x80x9cImproved High Performance Polymer Compositions,xe2x80x9d with the named inventors Thomas W. Smith, Timothy J. Fuller, Ram S. Narang, and David J. Luca, and European Patent Publication 0,827,029, the disclosures of each of which are totally incorporated herein by reference, disclose a composition comprising a polymer with a weight average molecular weight of from about 1,000 to about 65,000, said polymer containing at least some monomer repeat units with a first, photosensitivity-imparting substituent which enables crosslinking or chain extension of the polymer upon exposure to actinic radiation, said polymer also containing a second, thermal sensitivity-imparting substituent which enables further polymerization of the polymer upon exposure to temperatures of about 140xc2x0 C. and higher, wherein the first substituent is not the same as the second substituent, said polymer being selected from the group consisting of polysulfones, polyphenylenes, polyether sulfones, polyimides, polyamide imides, polyarylene ethers, polyphenylene sulfides, polyarylene ether ketones, phenoxy resins, polycarbonates, polyether imides, polyquinoxalines, polyquinolines, polybenzimidazoles, polybenzoxazoles, polybenzothiazoles, polyoxadiazoles, copolymers thereof, and mixtures thereof.
Copending application U.S. Ser. No. 08/697,761, filed Aug. 29, 1996, entitled xe2x80x9cProcess for Direct Substitution of High Performance Polymers with Unsaturated Ester Groups,xe2x80x9d with the named inventors Timothy J. Fuller, Ram S. Narang, Thomas W. Smith, David J. Luca, and Raymond K. Crandall, and European Patent Publication 0,827,030, the disclosures of each of which are totally incorporated herein by reference, disclose a process which comprises reacting a polymer of the general formula 
wherein x is an integer of 0 or 1, A is one of several specified groups, such as 
B is one of several specified groups, such as 
or mixtures thereof, and n is an integer representing the number of repeating monomer units, with (i) a formaldehyde source, and (ii) an unsaturated acid in the presence of an acid catalyst, thereby forming a curable polymer with unsaturated ester groups. Also disclosed is a process for preparing an ink jet printhead with the above polymer.
Copending application U.S. Ser. No. 08/705,479, filed Aug. 29, 1996, entitled xe2x80x9cProcesses for Substituting Haloalkylated Polymers With Unsaturated Ester, Ether, and Alkylcarboxymethylene Groups,xe2x80x9d with the named inventors Timothy J. Fuller, Ram S. Narang, Thomas W. Smith, David J. Luca, and Raymond K. Crandall, and European Patent Publication 0,827,026, the disclosures of each of which are totally incorporated herein by reference, disclose a process which comprises reacting a haloalkylated aromatic polymer with a material selected from the group consisting of unsaturated ester salts, alkoxide salts, alkylcarboxylate salts, and mixtures thereof, thereby forming a curable polymer having functional groups corresponding to the selected salt. Another embodiment of the invention is directed to a process for preparing an ink jet printhead with the curable polymer thus prepared.
Copending application U.S. Ser. No. 08/705,376, filed Aug. 29, 1996, entitled xe2x80x9cBlends Containing Curable Polymers,xe2x80x9d with the named inventors Ram S. Narang and Timothy J. Fuller, and European Patent Publication 0,827,031, the disclosures of each of which are totally incorporated herein by reference, disclose a composition which comprises a mixture of (A) a first component comprising a polymer, at least some of the monomer repeat units of which have at least one photosensitivity-imparting group thereon, said polymer having a first degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram and being of the general formula 
wherein x is an integer of 0 or 1, A is one of several specified groups, such as 
B is one of several specified groups, such as 
or mixtures thereof, and n is an integer representing the number of repeating monomer units, and (B) a second component which comprises either (1) a polymer having a second degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram lower than the first degree of photosensitivity-imparting group substitution, wherein said second degree of photosensitivity-imparting group substitution may be zero, wherein the mixture of the first component and the second component has a third degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram which is lower than the first degree of photosensitivity-imparting group substitution and higher than the second degree of photosensitivity-imparting group substitution, or (2) a reactive diluent having at least one photosensitivity-imparting group per molecule and having a fourth degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram, wherein the mixture of the first component and the second component has a fifth degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram which is higher than the first degree of photosensitivity-imparting group substitution and lower than the fourth degree of photosensitivity-imparting group substitution; wherein the weight average molecular weight of the mixture is from about 10,000 to about 50,000; and wherein the third or fifth degree of photosensitivity-imparting group substitution is from about 0.25 to about 2 milliequivalents of photosensitivity-imparting groups per gram of mixture. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned composition.
Copending application U.S. Ser. No. 08/705,372, filed Aug. 29, 1996, entitled xe2x80x9cHigh Performance Curable Polymers and Processes for the Preparation Thereof,xe2x80x9d with the named inventors Ram S. Narang and Timothy J. Fuller, and European Patent Publication 0,827,033, the disclosures of each of which are totally incorporated herein by reference, disclose a composition which comprises a polymer containing at least some monomer repeat units with photosensitivity-imparting substituents which enable crosslinking or chain extension of the polymer upon exposure to actinic radiation, said polymer being of the formula 
wherein x is an integer of 0 or 1, A is one of several specified groups, such as 
B is one of several specified groups, such as 
or mixtures thereof, and n is an integer representing the number of repeating monomer units, wherein said photosensitivity-imparting substituents are allyl ether groups, epoxy groups, or mixtures thereof. Also disclosed are a process for preparing a thermal ink jet printhead containing the aforementioned polymers and processes for preparing the aforementioned polymers.
Copending application U.S. Ser. No. 08/705,490, filed Aug. 29, 1996, entitled xe2x80x9cHalomethylated High Performance Curable Polymers,xe2x80x9d with the named inventors Ram S. Narang and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses a process which comprises the steps of (a) providing a polymer containing at least some monomer repeat units with halomethyl group substituents which enable crosslinking or chain extension of the polymer upon exposure to a radiation source which is electron beam radiation, x-ray radiation, or deep ultraviolet radiation, said polymer being of the formula 
wherein x is an integer of 0 or 1, A is one of several specified groups, such as 
B is one of several specified groups, such as 
or mixtures thereof, and n is an integer representing the number of repeating monomer units, and (b) causing the polymer to become crosslinked or chain extended through the photosensitivity-imparting groups. Also disclosed is a process for preparing a thermal ink jet printhead by the aforementioned curing process.
Copending application U.S. Ser. No. 08/697,760, filed Aug. 29, 1996, entitled xe2x80x9cAqueous Developable High Performance Curable Polymers,xe2x80x9d with the named inventors Ram S. Narang and Timothy J. Fuller, and European Patent Publication 0,827,032, the disclosures of each of which are totally incorporated herein by reference, disclose a composition which comprises a polymer containing at least some monomer repeat units with water-solubility-imparting substituents and at least some monomer repeat units with photosensitivity-imparting substituents which enable crosslinking or chain extension of the polymer upon exposure to actinic radiation, said polymer being of the formula 
wherein x is an integer of 0 or 1, A is one of several specified groups, such as 
B is one of several specified groups, such as 
or mixtures thereof, and n is an integer representing the number of repeating monomer units. In one embodiment, a single functional group imparts both photosensitivity and water solubility to the polymer. In another embodiment, a first functional group imparts photosensitivity to the polymer and a second functional group imparts water solubility to the polymer. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned polymers.
New photoresists have been discovered which can, in many instances, provide results superior to polyimides. These photoresists include polyarylene ethers, polyarylene ether ketones, polyarylene ether sulfones, and the like. Accordingly, while known compositions and processes are suitable for their intended purposes, a need remains for adhesion promoters particularly suitable for use with polyarylene photoresists. In addition, a need remains for adhesion promoters suitable for use with a wide variety of polymeric photoresists. Further, a need remains for adhesion promoters which enable good interfacial adhesion of photopatternable polymer films on surfaces such as metal, plasma nitride, silicon, and glass, including glass doped with phosphorus and/or boron. Additionally, a need remains for adhesion promoters which enable the formation of protective layers and fluid paths in ink jet printheads that are highly resistant to hydrolysis degradation. There is also a need for ink jet printheads which are resistant to delamination when exposed to aqueous inks having basic pH. In addition, a need remains for adhesion promoters in photopatternable articles which provide good layer adhesion during the development process during which portions of the photopatternable material are removed in an imagewise pattern, thereby reducing or eliminating undercutting and floating images (wherein portions of the photopatternable material which should remain intact become delaminated). Further, a need remains for adhesion promoters which have surface energies and surface characteristics that enable good wetting of the adhesion promoter surface by photopatternable polymers.
It is an object of the present invention to provide adhesion promoters and ink jet printheads with the above noted advantages.
It is another object of the present invention to provide adhesion promoters particularly suitable for use with polyarylene photoresists.
It is yet another object of the present invention to provide adhesion promoters suitable for use with a wide variety of polymeric photoresists.
It is still another object of the present invention to provide adhesion promoters which enable good interfacial adhesion of photopolymer films on surfaces such as metal, plasma nitride, silicon, and glass, including glass doped with phosphorus and/or boron.
Another object of the present invention is to provide adhesion promoters which enable the formation of protective layers and fluid paths in ink jet printheads that are highly resistant to hydrolysis degradation.
Yet another object of the present invention is to provide ink jet printheads which are resistant to delamination when exposed to aqueous inks having basic pH.
Still another object of the present invention is to provide adhesion promoters in photopatternable articles which provide good layer adhesion during the development process during which portions of the photopatternable material are removed in an imagewise pattern, thereby reducing or eliminating undercutting and floating images (wherein portions of the photopatternable material which should remain intact become delaminated).
It is another object of the present invention to provide adhesion promoters which have surface energies and surface characteristics that enable good wetting of the adhesion promoter surface by photopatternable polymers.
These and other objects of the present invention (or specific embodiments thereof) can be achieved by providing a process for bonding a first article to a second article which comprises (a) providing a first article comprising a polymer having photosensitivity-imparting substituents; (b) providing a second article comprising metal, plasma nitride, silicon, or glass; (c) applying to at least one of the first article and the second article an adhesion promoter selected from silanes, titanates, or zirconates having (i) alkoxy, aryloxy, or arylalkyloxy functional groups and (ii) functional groups including at least one photosensitive aliphatic  greater than Cxe2x95x90C less than  linkage; (d) placing the first article in contact with the second article; and (e) exposing the first article, second article, and adhesion promoter to radiation, thereby bonding the first article to the second article with the adhesion promoter. Another embodiment of the present invention is directed to an ink jet printhead which comprises (i) an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles, (ii) a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes formed thereon, at least a portion of said surface comprising metal, plasma nitride, silicon, or glass, and (iii) an insulative layer deposited on the surface of the lower substrate and over the heating elements and addressing electrodes and patterned to form recesses therethrough to expose the heating elements and terminal ends of the addressing electrodes, the upper and lower substrates being aligned, mated, and bonded together to form the printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles, said insulative layer comprising a crosslinked or chain extended polymer wherein the crosslinking or chain extension is at least partly through photosensitivity-imparting substituents; said insulative layer being bonded to the surface of the lower substrate with an adhesion promoter selected from silanes, titanates, or zirconates having (a) alkoxy, aryloxy, or arylalkyloxy functional groups and (b) functional groups including at least one photosensitive aliphatic  greater than Cxe2x95x90C less than  linkage. Yet another embodiment of the present invention is directed to a process for forming an ink jet printhead which comprises (a) providing a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes having terminal ends formed thereon, at least a portion of said surface comprising metal, plasma nitride, silicon, or glass; (b) depositing onto the surface of the lower substrate having the heating elements and addressing electrodes thereon an adhesion promoter selected from silanes, titanates, or zirconates having (i) alkoxy, aryloxy, or arylalkyloxy functional groups and (ii) functional groups including at least one photosensitive aliphatic  greater than Cxe2x95x90C less than  linkage; (c) exposing the adhesion promoter and the insulative layer to actinic radiation in an imagewise pattern such that the polymer comprising the insulative layer in exposed areas becomes crosslinked or chain extended and the polymer in unexposed areas does not become crosslinked or chain extended, wherein the unexposed areas correspond to areas of the lower substrate having thereon the heating elements and the terminal ends of the addressing electrodes, and wherein the insulative layer is bonded to the lower substrate with the adhesion promoter in exposed areas; (d) removing the adhesion promoter and the polymer from the unexposed areas, thereby forming recesses in the layer, said recesses exposing the heating elements and the terminal ends of the addressing electrodes; (e) providing an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles; and (f) aligning, mating, and bonding the upper and lower substrates together to form a printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles, thereby forming a thermal ink jet printhead. Still another embodiment of the present invention is directed to an ink jet printhead which comprises (i) an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles, (ii) a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes formed thereon, at least a portion of said surface comprising metal, plasma nitride, silicon, or glass, and (iii) an insulative layer deposited on the surface of the lower substrate and over the heating elements and addressing electrodes and patterned to form recesses therethrough to expose the heating elements and terminal ends of the addressing electrodes, the upper and lower substrates being aligned, mated, and bonded together to form the printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles, said insulative layer comprising (a) a crosslinked or chain extended polymer wherein the crosslinking or chain extension is at least partly through photosensitivity-imparting substituents, and (b) an adhesion promoter selected from silanes, titanates, or zirconates having (1) alkoxy, aryloxy, or arylalkyloxy functional groups and (2) functional groups including at least one photosensitive aliphatic  greater than Cxe2x95x90C less than  linkage. Another embodiment of the present invention is directed to a process for forming an ink jet printhead which comprises (a) providing a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes having terminal ends formed thereon, at least a portion of said surface comprising metal, plasma nitride, silicon, or glass; (b) depositing onto the surface of the lower substrate an insulative layer comprising (i) a polymer having photosensitivity-imparting substituents, and (ii) an adhesion promoter selected from silanes, titanates, or zirconates having (A) alkoxy, aryloxy, or arylalkyloxy functional groups and (B) functional groups including at least one photosensitive aliphatic  greater than Cxe2x95x90C less than  linkage; (c) exposing the insulative layer to actinic radiation in an imagewise pattern such that the polymer comprising the insulative layer in exposed areas becomes crosslinked or chain extended and the polymer in unexposed areas does not become crosslinked or chain extended, wherein the unexposed areas correspond to areas of the lower substrate having thereon the heating elements and the terminal ends of the addressing electrodes, and wherein the insulative layer is bonded to the lower substrate in exposed areas; (d) removing the adhesion promoter and the polymer from the unexposed areas, thereby forming recesses in the layer, said recesses exposing the heating elements and the terminal ends of the addressing electrodes; (e) providing an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles; and (f) aligning, mating, and bonding the upper and lower substrates together to form a printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nobles, thereby forming a thermal ink jet printhead.